I have had some patience for Corbyn, but I don't see how anyone can defend him staying any longer. There is very likely to be a general election in October, regardless of who wins the Conservative nomination. Right now, the Parliamentary Labour Party will not stand for Corbyn. You may disagree with this. If so, your only way to change this is to start a deselection process. If that happened right now, the party would split; there are simply too many anti-Corbyn MPs to make that kind of shift possible. That would mean ceding the general election to the Conservatives. Given this election will almost certainly be fought on the topic of Europe, that is absolutely unconscionable; this is perhaps the very final chance to avert a catastrophic sequence of events for the United Kingdom, far beyond the consequences of any normal election.
Normally, I'd be a Starmer man, or perhaps Nandy. Certainly, I'm on the left of the party. But right now, we need Dan Jarvis. I can't see any compelling argument to the alternative.